Risky and unproven climate-changing technologies could have "catastrophic consequences" for the earth and humankind if used irresponsibly, according to a new report.

Yet without drastic further cuts in carbon dioxide emissions, a geoengineering solution may offer the only hope of saving the world from disastrous run-away global warming, experts warned.

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A report by the Royal Society, Britain's leading academic institution, looks at the feasibility and potential dangers of technologies designed to cool the earth.

They include artificial "trees" that suck carbon dioxide out of the air, and spraying sulphate particles high in the atmosphere to scatter the sun's rays into space. The scientists concluded that, although some approaches were possible, they had not yet been properly researched and posed serious potential dangers for the planet.

Professor John Shepherd, who chaired the Royal Society geoengineering working group, said: "It is an unpalatable truth that unless we can succeed in greatly reducing carbon dioxide emissions we are heading for a very uncomfortable and challenging climate future, and geoengineering will be the only option left to limit further temperature increases."

"Our research found that some geoengineering techniques could have serious unintended and detrimental effects on many people and ecosystems â€“ yet we are still failing to take the only action that will prevent us from having to rely on them."